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    <h2 id="antlib">Antlib</h2>

    <h3>Description</h3>
    <p>
      An antlib file is an xml file with a root element of <code>antlib</code>.  Antlib's elements
      are Apache Ant definition tasks&mdash;like <a href="../Tasks/taskdef.html">Taskdef</a> or any
      Ant task that
      extends <code class="code">org.apache.tools.ant.taskdefs.AntlibDefinition</code>.
    </p>
    <p>
      The current set of declarations bundled with Ant that do this are:
    </p>
    <ol>
      <li><a href="../Tasks/typedef.html">Typedef</a></li>
      <li><a href="../Tasks/taskdef.html">Taskdef</a></li>
      <li><a href="../Tasks/macrodef.html">Macrodef</a></li>
      <li><a href="../Tasks/presetdef.html">Presetdef</a></li>
      <li><a href="../Tasks/scriptdef.html">Scriptdef</a></li>
    </ol>
    <p>
      A group of tasks and types may be defined together in an antlib file. For example the
      file <samp>sample.xml</samp> contains the following:
    </p>
    <pre>
&lt;?xml version="1.0"?&gt;
&lt;antlib&gt;
    &lt;typedef name="if" classname="org.acme.ant.If"/&gt;
    &lt;typedef name="scriptpathmapper"
             classname="org.acme.ant.ScriptPathMapper"
             onerror="ignore"/&gt;
    &lt;macrodef name="print"&gt;
        &lt;attribute name="file"/&gt;
        &lt;sequential&gt;
            &lt;concat taskname="print"&gt;
                &lt;fileset dir="." includes="@{file}"/&gt;
            &lt;/concat&gt;
        &lt;/sequential&gt;
    &lt;/macrodef&gt;
&lt;/antlib&gt;</pre>
    <p>
      It defines two types or tasks, <code>if</code> and <code>scriptpathmapper</code>.  This
      antlib file may be used in a build script as follows:
    </p>
    <pre>&lt;typedef file="sample.xml"/&gt;</pre>
    <p>
      The other attributes of <code>&lt;typedef&gt;</code> may be used as well.  For example,
      assuming that the <samp>sample.xml</samp> is in a jar file <samp>sample.jar</samp> also
      containing the classes, the following build fragment will define the <code>if</code>
      and <code>scriptpathmapper</code> tasks/types and place them in the namespace
      uri <code>samples:/acme.org</code>.
    </p>
    <pre>
&lt;typedef resource="org/acme/ant/sample.xml"
         uri="samples:/acme.org"/&gt;</pre>
    <p>
      The definitions may then be used as follows:
    </p>
    <pre>
&lt;sample:if valuetrue="${props}" xmlns:sample="samples:/acme.org"&gt;
    &lt;sample:scriptpathmapper language="beanshell"&gt;
        some bean shell
    &lt;/sample:scriptpathmapper&gt;
&lt;/sample:if&gt;</pre>

    <h3 id="antlibnamespace">Antlib namespace</h3>
    <p>
      The name space URIs with the pattern <code>antlib:<i>java.package</i></code> are given
      special treatment.
    </p>
    <p>
      When Ant encounters a element with a namespace URI with this pattern, it will check to see
      if there is a resource of the name <samp>antlib.xml</samp> in the package directory in the
      default classpath.
    </p>
    <p>
      For example, assuming that the file <samp>antcontrib.jar</samp> has been placed in the
      directory <samp>${ant.home}/lib</samp> and it contains the
      resource <samp>net/sf/antcontrib/antlib.xml</samp> which has all antcontrib's definitions
      defined, the following build file will automatically load the antcontrib definitions at
      location <code>HERE</code>:
    </p>
    <pre>
&lt;project default="deletetest" xmlns:antcontrib="antlib:net.sf.antcontrib"&gt;
    &lt;macrodef name="showdir"&gt;
        &lt;attribute name="dir"/&gt;
        &lt;sequential&gt;
            &lt;antcontrib:shellscript shell="bash"&gt;  &lt;!-- HERE --&gt;
                ls -Rl @{dir}
            &lt;/antcontrib:shellscript&gt;
        &lt;/sequential&gt;
    &lt;/macrodef&gt;

    &lt;target name="deletetest"&gt;
        &lt;delete dir="a" quiet="yes"/&gt;
        &lt;mkdir dir="a/b"/&gt;
        &lt;touch file="a/a.txt"/&gt;
        &lt;touch file="a/b/b.txt"/&gt;
        &lt;delete&gt;
            &lt;fileset dir="a"/&gt;
        &lt;/delete&gt;
        &lt;showdir dir="a"/&gt;
    &lt;/target&gt;
&lt;/project&gt;</pre>
    <p>
      The requirement that the resource is in the default classpath may be removed in future
      versions of Ant.
    </p>
    <h3 id="loadFromInside">Load antlib from inside of the buildfile</h3>
    <p>
      If you want to separate the antlib from your local Ant installation, e.g. because you want
      to hold that jar in your project's SCM system, you have to specify a classpath, so that
      Ant could find that jar. The best solution is loading the antlib
      with <code>&lt;taskdef&gt;</code>.
    </p>
    <pre>
&lt;project xmlns:<span style="color:green">antcontrib</span>="<span style="color:red">antlib:net.sf.antcontrib</span>"&gt;
    &lt;taskdef uri="<span style="color:red">antlib:net.sf.antcontrib</span>"
             resource="net/sf/antcontrib/antlib.xml"
             classpath="path/to/ant-contrib.jar"/&gt;

    &lt;target name="iterate"&gt;
        &lt;<span style="color:green">antcontrib</span>:for param="file"&gt;
            &lt;fileset dir="."/&gt;
            &lt;sequential&gt;
                &lt;echo message="- @{file}"/&gt;
            &lt;/sequential&gt;
        &lt;/antcontrib:for&gt;
    &lt;/target&gt;
&lt;/project&gt;</pre>
    <h3 id="currentnamespace">Current namespace</h3>
    <p>
      Definitions defined in antlibs may be used in antlibs. However, the namespace that
      definitions are placed in are dependent on the <code>&lt;typedef&gt;</code> that uses the
      antlib. To deal with this problem, the definitions are placed in the namespace
      URI <code>ant:current</code> for the duration of the antlib execution.  For example, the
      following antlib defines the task <code>&lt;if&gt;</code>, the
      type <code>&lt;isallowed&gt;</code> and a macro <code>&lt;ifallowed&gt;</code> that makes
      use of the task and type:
    </p>
    <pre>
&lt;antlib xmlns:current="ant:current"&gt;
    &lt;taskdef name="if" classname="org.acme.ant.If"/&gt;
    &lt;typedef name="isallowed" classname="org.acme.ant.Isallowed"/&gt;
    &lt;macrodef name="ifallowed"&gt;
        &lt;attribute name="action"/&gt;
        &lt;element name="do"/&gt;
        &lt;sequential&gt;
            &lt;current:if&gt;
                &lt;current:isallowed test="@{action}"/&gt;
                &lt;current:then&gt;
                    &lt;do/&gt;
                &lt;/current:then&gt;
            &lt;/current:if&gt;
        &lt;/sequential&gt;
    &lt;/macrodef&gt;
&lt;/antlib&gt;</pre>
    <h3>Other examples and comments</h3>
    <p>
      Antlibs may make use of other antlibs.
    </p>
    <p>
      As the names defined in the antlib are in the namespace URI as specified by the
      calling <code>&lt;typedef&gt;</code> or by automatic element resolution, one may reuse
      names from core Ant types and tasks, provided the caller uses a namespace URI. For
      example, the following antlib may be used to define defaults for various tasks:
    </p>
    <pre>
&lt;antlib xmlns:antcontrib="antlib:net.sf.antcontrib"&gt;
    &lt;presetdef name="javac"&gt;
        &lt;javac deprecation="${deprecation}"
               debug="${debug}"/&gt;
    &lt;/presetdef&gt;
    &lt;presetdef name="delete"&gt;
        &lt;delete quiet="yes"/&gt;
    &lt;/presetdef&gt;
    &lt;presetdef name="shellscript"&gt;
        &lt;antcontrib:shellscript shell="bash"/&gt;
    &lt;/presetdef&gt;
&lt;/antlib&gt;</pre>
    <p>
      This may be used as follows:
    </p>
    <pre>
&lt;project xmlns:local="localpresets"&gt;
    &lt;typedef file="localpresets.xml" uri="localpresets"/&gt;
    &lt;local:shellscript&gt;
        echo "hello world"
    &lt;/local:shellscript&gt;
&lt;/project&gt;</pre>

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